The present invention relates to an apparatus and method for improving the presentation of information on a video display, and is particularly directed to an improved means and method for presenting and comparing data displayed on the faceplate of a cathode ray tube in graphic form.
In electrical testing perhaps the most common parameter monitored is the voltage-current (V-I) characteristic of the component or device. This parameter is generally derived by applying a changing voltage across the component, or a select portion of a device, and measuring the output current therefrom. The voltage is typically varied in a linear manner from 0 volts up to a predetermined, maximum voltage, and then reduced in a linear manner to the starting voltage. The output current is then measured and displayed.
The information thus displayed typically not only includes the performance of the device under test, but also the operation of a reference, or "ideal", device. Thus, two sets of data are displayed, from a comparison of which the operation of the device under test may be accurately determined. Frequently the graphical presentations of performance data for the two devices may closely approach one another and perhaps, at least partially, overlap. Thus, it may be difficult, if not impossible, to determine which device is associated with a particular performance curve. In some applications, this information may be critical for proper operation of the system in which the component or device is to be utilized.
Prior art systems provide for the comparison of a device under test with a known, good device by switching the CRT display from one device to the other and back again. The switching may be accomplished either manually or by timed-based automatic switching. In either case, a side-by-side comparison for more accurate evaluation is unavailable. In earlier displays, a chopper circuit is used to multiplex the two channel inputs for the simultaneous display of both sets of data. This, however, is of limited use where the data presentations are virtually identical and nearly completely overlapped.
The present invention is intended to overcome the aforementioned limitations of the prior art by providing a means and method for displaying and accurately comparing performance data in graphic form of an electrical component or device under test with that of a reference, or "ideal", component or device.